Short-Circuit Current Calculator

How Short-Circuit Current works

The calculation starts with Ifault = V ÷ Z. Short-Circuit Current uses Source voltage, Total fault impedance to report Prospective fault current.

With the loaded values, prospective fault current evaluates to 657.14 A. Change only the quantity being investigated.

Inputs for Short-Circuit Current

Source voltage and Total fault impedance belong to Short-Circuit Current. Keep source units with source voltage.

The preset case is instructional rather than prescriptive. Enter the applicable electrical data. For current per conductor, use Parallel Conductor Sharing Calculator.

Source voltage

Example entry: 230 V.

Total fault impedance

Example entry: 0.35 Ω.

Reading the Short-Circuit Current result

This output represents Short-Circuit Current. If the next question concerns derated ampacity, open Conductor Temperature Derating Calculator.

Standard size, duty, temperature, and transient checks remain outside this single equation.

Measurement and units

Treat these results as planning arithmetic; conductor and protective-device selection must follow the applicable electrical code and equipment instructions. Check prefixes on source voltage.

Keep the same electrical reference points across saved cases.

Limits of this calculation

The protective device interrupting rating must exceed prospective current.

A complete system can contain effects that this equation does not represent. Unentered effects remain outside Short-Circuit Current. Use Contact Resistance Loss Calculator as the follow-up for contact power loss.

A useful Short-Circuit Current comparison

Record prospective fault current before testing a different source voltage value. Minimum circuit rating belongs in the separate Continuous Load Capacity worksheet.

Document the alternate source voltage source.